diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -1428,7 +1428,7 @@ class Test(unittest.TestCase):
             )
             hgrc.write(b'[web]\n')
             hgrc.write(b'address = localhost\n')
-            hgrc.write(b'ipv6 = %s\n' % str(self._useipv6).encode('ascii'))
+            hgrc.write(b'ipv6 = %r\n' % self._useipv6)
             hgrc.write(b'server-header = testing stub value\n')
 
             for opt in self._extraconfigopts: